Continuously adjustable lifting devices

ABSTRACT

The invention provides a lifting device or displacement controlling and locking device for height adjustment of table tops and other members. The device comprises a double tubular housing having in the inner tube a piston the position of which is controllable and lockable by controlling flow of fluid from one side of the piston to the other through a by-pass passage provided between the inner and outer tubes. A blocking device at one end of the housing is operable to allow the by-pass flow when height adjustment is required.

nited States Patent Bauer 151 3, 66,593 1 Apr. 18, 11972 [54] CONTINUOUSLY ADJUSTABLE LIF TING DEVICES [72] Inventor: Fritz Bauer, 14 Schulzstrasse, D-8503,

Altdorf near Nuremberg, Germany [22] Filed: Dec. 2, 1969 [21] Appl. No.: 881,436

[30] Foreign Application Priority Date Dec. 3, 1968 Germany ..P 18 12 282.2

[52] US. Cl. ..188/300, 248/354 H, 297/355 [51] Int. Cl ..F16f 9/32 [58] Field of Search ..188/300, 313, 318;248/354 H; 297/355 [56] References Cited UNITED STATES PATENTS 2,042,443 5/1936 Buckstone ..248/354 H 2,658,588 11/1953 Kanuch ..188/300 2,897,613 8/1959 Davidson et a1. ..188/300 X 3,223,206 12/1965 Bainbridge et al ..188/300 3,281,107 10/1966 Lewis ..248/354 H 3,407,909 10/1968 Seckerson et al ..188/313 Primary Examiner-George E. A. Halvosa Attorney-Keith Misegades and George R. Douglas, Jr.

[57] ABSTRACT The invention provides a lifting device or displacement controlling and locking device for height adjustment of table tops and other members. The device comprises a double tubular housing having in the inner tube a piston the position of which is controllable and lockable by controlling flow of fluid from one side of the piston to the other through a by-pass passage provided between the inner and outer tubes. A blocking device at one end of the housing is operable to allow the bypass flow when height adjustment is required.

6 Claims, 1 Drawing lFigure CONTINUOUSLY ADJUSTABLE LIFIING DEVICES The invention relates to a lifting device for the stepless height adjustment of table tops, chair seats and the like. Such a lifting device chosen out of a plurality of lifting devices and forming the basis of the invention consists of a tubular housing having a gas and/or liquid filling, with an axially displaceable piston sealed in relation to it and provided on a rod, plunger or the like which sealingly extends out of one end of the housing, and a locking device operable from the outside, for locking an adjusted position is provided in the flow opening for the housing contents, connecting the housing chamber in front of the piston with the housing chamber behind the piston.

Such a lifting device e.g. known from German utility model specification 1,960,813 has the advantage that the displacement path for the table top, the chair seat or the like corresponds practically to the clear overall length of the tubular housing. In this connection, the rod, the plunger or the like connected with the piston and extending out of the housing, is connected in the usual way with its free end or their free ends to the table top or on to the chair seat or the like, and the end of the housing remote from the piston rod is built fixedly into the table frame or into the base of the chair or the like. For setting a desired height, the locking device which locks the instantaneous position of the table top or of the chair seat is opened, so that the contents of the housing instead of acting against the displacing movement, can flow through the flow opening from one housing chamber into the other housing chamber so that depending on the piston movement, one of the housing chambers increases in volume and the other housing chamber decreases in volume. Of course, both housing chambers together correspond in their volume always with the constant total contents of the housing of the lifting device. When the desired new position of the table top, chair seat or the like has been reached, then by closing the flow opening by means of the externally operable locking device, the new position is locked.

In this known lifting device, the flow opening with the locking device, is built into the axially displaceable piston which is sealed relative to the inner wall of the housing. Opening and closing of the flow opening is effected by means of a slide which controls an axial opening of the piston. The slide is moved by an actuating rod which is displaceable in the hollow piston rod which is adjustable e.g. by a lever linkage at its free end. It is very difficult to seal the slide. Such a construction is.

relatively uneconomic, since the piston rod has to be bored out. Moreover, compared with the solid actuating rod, such a hollow bored rod acts differently, e.g. during hardening, so that as a result of this, relatively many work pieces have to be rejected as unusable. Finally, the piston of the known lifting device requires a special hub for providing the necessary radial bores which open into the axial bore, and for fixing of the hollow piston rod. The displacement path is shortened by the height of this hub however, so that the clear overall length of tl-le housing is not inconsiderably larger than the displacement path of the lifting device, quite apart from the fact that the latter also requires considerable structural expense and imposes difficult sealing conditions.

A lifting device which is extremely simple in construction is known, e.g. from German utility model specification 1,924,528, which has a locking device which is easy to seal, and a solid piston rod. The tubular housing is however subdivided into three housing chambers one of which is provided between the flat end face of the piston provided with the solid piston rod and a fixed separating wall, the second housing chamber serves as the supply chamber and is disposed between the latter and an axially displaceable separating piston and the third housing chamber is simply filled with pressure gas and is disposed between the separating piston and a plug closing the housing at the adjacent end. The separating wall is bridged by means of a flow channel which can be closed by means of a tap valve in order to be able to bypass the pressure liquid in the housing chamber lying in front of the piston into the housing chamber lying behind the fixed separating wall, or reversely, for effecting the displacement in height.

Moreover, in the piston an axial bore is also provided which is automatically influenced by a valve plate so as to be able to fill the housing chamber on the piston rod side with pressure fluid or empty it through the piston.

The known lifting device thus has a clear housing length which is considerably greater than the actual stroke or largest displacement path. Consequently, its range of use is essentially restricted. More particularly however, the building in of this lifting device is made extremely complicated or is made practically impossible, by the bypass channel with locking device arranged outside the housing, since in a telescopically constructed table or chair base, insufficient space is available for these separate outwardly projecting components. Also, the axially displaceable separating piston and the fixedly built in separating wall represent an additional structural and working expense which unfavorably influences the manufacture, so that also this known lifting device is not satisfactory.

The object of the invention, however, is to construct the known lifting device for the stepless height adjustment of table tops, chair seats and the like, with a gas and/or liquid filled housing for receiving an axially displaceable piston on an outwardly guided rod and with a blocking device operable from the outside and arranged in a flow opening connecting the housing chamber in front of the piston with the housing chamber behind the piston, in such a way that with a practically complete utilisation of the clear housing length as the displacement path, a considerably simpler construction with individual components which are easy to seal and manufacture, is enabled.

According to the invention, this object is achieved in an advantageous manner, in that the blocking device is arranged in the end of the housing lying opposite to that in which the guiding and sealing means for the piston rod are provided, and that a by-pass chamber surrounding the housing and extending along the entire length thereof is connected to the flow open ing for connecting the housing chamber in front of the piston with the housing chamber behind the piston.

The details of the construction may be such that the blocking device is arranged in a double base of the housing and is formed by a release pin which is guided so as to extend outwardly and which can be axially displaced from the outside, the pin having a head at its inner end and being guided in seals in oppositely lying regions of the two base portions of the double base, which between them include a by-pass chamber, the pin having a peripheral groove between the seals, the groove having two frusto-conical side walls widening outwardly, the inner base of the said double base having a bore on the housing side of the seal, which is greater in diameter than the diameter of the pin and which opens into the housing chamber. The housing is in this case formed by two steel tubes which are concentric and pushed one into the other, defining the radial width of the by-pass chamber by their different diameters, the outer steel tube being connected by one end to the periphery of the outer base of the double base, and the other steel tube being connected to the appropriately stepped periphery of the inner base of the double base, the other oppositely lying ends being fixed in a similar manner gas and liquid tightly to the plug receiving the seals for the rod, plunger or the like of the piston. The plug has an annular chamber connected with the housing chamber behind the piston, which is connected through at least one radial bore with the by-pass chamber extending beyond the fixing position of the inner steel tube onto the plug. At the other end of the housing, the bypass region extending somewhat into the inner base from between the two base portions of the double base is connected by at least one axial bore with the by-pass chamber formed between the two steel pipes of the housing.

By these measures, a lifting device is provided which is externally smooth on all sides and which consequently can be conveniently installed, the overall structural length of which only slightly exceeds the displacement path of the piston rod, or of the plunger or the like. More particularly, the lifting device constructed according to the invention has a simple disc-shaped piston having a seal only on its outer periphery, which can be secured by means of a suitable bore, on a stud portion of the solid piston rod, plunger or the like, in a simple manner without unfavourably influencing the available displacement path. The blocking device which is readily operable from below in the conventional manner by means of a lever linkage, comprises a release pin the dimensions of which are not subject to any precise limits and which nevertheless can be easily sealed. A further essential advantage is that with pressure gas filling of the housing, the addition of a small amount of oil as lubricant is sufficient, since in the lifting device when it has been built into its place of use, the piston rod always extends downwardly towards the floor so that the oil or lubricant remains in the lower part of the housing under the action of gravity. By this arrangement, a satisfactory lubrication of the piston and piston rod or plunger is ensured and as a result of this the lifting device has a long life duration. Since its individual components have a simple shape which does not distort on subsequent treatment, e.g. hardening, or in which a slight change in shape would be without deleterious effect, the manufacture of the device is extremely economic.

In order to make the invention clearly understood, reference will now be made to the accompanying drawing which is given by way of example and which is a longitudinal sectional view through a lifting device of the invention, showing a piston rod thereof in its maximum extended position.

Each hydraulic or hydro-pneumatic lifting device forming the basis of the invention comprises a housing 11 which essentially consists of two concentrically disposed steel tubes 12 and 13 of different diameters. At one end the housing is gas or liquid tightly closed by a double base 14 and at the other end by a plug 15. In the inner steel tube 12, a piston 16 is axially displaceably guided, and the piston is fixed by means of a hollow stud 17 onto a piston rod 18, a plunger or the like which extends in a gas or liquid tight manner through the plug. The double base comprises two individual base portions 19 and 20 which enclose between them a by-pass or deflectlon region 21, the greater part of the deflection region being disposed in the outer base portion 19 and only a small part of the deflection region 21 extends into the inner base portion 20. A releasing pin 22 is axially displaceably guided in a sealed manner, coaxially in the two base portions, its inner end having a head 23 serving as an abutment the pin extending with its other end outwardly from a boss 24 of the outer base portion 19, which is preferably provided with an external thread. The outwardly extending end of the pin 22 is arranged for engagement by a lever linkage in the form of a double armed lever which serves as an actuating element for axial displacement of the release pin, the boss 19 of the outer base portion serving for abutment on a boss, a projection or the like of a table top, chair seat or other plate like member.

Both base portions 19 and 20 have cylindrical pot-shaped recesses 25 or 26 in their sides which face each other, the margins 26 of the openings which face each other being widened towards the inside, in a somewhat frusto-conical manner. The cylindrically extending part has a depth which corresponds to the height extending parallel to the longitudinal axis of a sealing ring 27 with an ideal rectangular cross-section. The ring surface facing the deflection region 21, of each sealing ring, is notched substantially v-shaped in cross-section so that the inner ring wall which surrounds and guides the release pin 22 is considerably smaller in height than the outer ring wall of each sealing ring. The pressure of the housing contents presses on each sealing ring in dependence on the v-shaped notching so that the considerably higher ring wall is pressed with essentially greater force into the cylindrically pot-shaped recess than is the significantly lower ring wall pressed on the shank of the release pin 22, so that with axial displacement of this release pin the two sealing rings 27 cannot be moved out of their seats. In both base portions, the sealing rings serve not only for sealing but also additionally for guiding the release pin, the bore receiving the release pin in the outer base portion having a diameter which ensures a sliding or displacing of the release pin.

The release pin 22, which essentially forms the blocking device for the housing chamber 28 lying in front of the piston 16, has an annular groove 29 disposed between the regions engaged by the two sealing rings 27. The groove 29 has frustoconically shaped outwardly extending side walls 30. The annular groove 29 co-operates with an axial bore 31 provided in the inner base portion 20 next to the respective seal of the release pin, and opens into the housing chamber 28. This bore 31 has a somewhat larger diameter than the shank diameter of the release pin which passes coaxially through this bore. If for the height adjustment of the lifting device, the release pin is pushed into the housing, then the housing contents, under the action of the piston movement, flow through this bore 31 into the deflection chamber 21 through the open annular groove 29 which is now adjoining.

The inner steel tube 12 carrying the piston 16 is arranged with its end facing the blocking device gas and liquid tightly disposed on a reduced diameter peripheral portion 32 of the inner base portion 20, if desired with the use of a sealing ring 33. The outer steel tube 13, which surrounds the inner steel tube leaving an annular gap-shaped surrounding chamber 34, extends over the outer periphery of the inner base portion 20 and receives a centralizing rim 35 of the abutting outer base portion 19, with which it is gas and liquid tightly connected. By the dimensional difference of the inner diameter of the outer steel tube and the outer diameter of the inner steel tube, the radial width of the by-pass chamber 34 is determined. The by-pass chamber 34 is connected by at least one axial flow opening 36 in the inner base portion 20 of the double base 14, with the part of the deflection chamber 21 which extends somewhat into this, through which any of the contents of the housing present in the deflection chamber and standing under pressure, passes into the by-pass chamber. For introducing the container contents e.g. compressed gas and oil, the outer base portion 19 may for example be provided with a threaded closure 37.

At the other end of the housing 11, the plug 15 is stepped to the inner diameter of the inner steel tube 12 so that a centralizing region 38 results, which extends into the inner steel tube. The outer steel tube 13 extends over the outer periphery of the plug which is common to both steel tubes, and is secured to this in a gas and liquid tight manner. The bore in the plug carrying the piston rod 18, the plunger or the like is provided with a seal 39 in which the piston rod 18 is slidingly sealed. The bore 40 which extends towards the inside of the housing at the inner end of the plug has a larger diameter than the piston rod, plunger or the like, so that the pressure medium can flow out of the expansion chamber formed as an annular groove 41 in the plug, into the housing chamber 42 disposed behind the piston 16. The by-pass chamber 34 is extended beyond the fixing point of the inner steel tube 12 formed by the centralizing portion 38, so that the by-pass chamber 34 can be connected with the annular chamber 41 constituting the expansion chamber in the plug, by at least one radial bore 43.

If for example the lifting device which is illustrated in the drawing in substantially its fully drawn out position is required to be shortened, that is to say the height of a table top, or a chair seat is required to be steplessly reduced, then by means of the lever linkage which is not illustrated, the blocking device is opened by pushing a release pin 22 into the housing. By pushing down the tabletop, chair seat or the like by hand, the piston 16 drives the housing contents disposed in front of the piston, through the deflection chamber 21 and through the flow opening 36 into the by-pass chamber 34 and from there through the radial bores 43 into the annular chamber 41 of the plug 15, from where it can pass through the axial bore 40 into the housing chamber 42 behind the piston. On steplessly reaching the desired height of the table top, chair seat or the like, the blocking device is again closed, whereupon due to the loading of the housing contents, for example compressed gas, tHe table top or the chair seat is locked in the new position.

lclaim:

1. A continuously adjustable lifting device for table tops, chair seats or the like, comprising a tubular casing containing a gas and/or liquid filling, a rod plunger means sealed in and protruding from an end of said casing, a blocking device operable from outside said casing and being arranged at the other end of said casing for locking said rod plunger means relative to said casing in an adjustable position, said blocking device provided in an overflow opening for the filling of the casing connecting the casing space before the plunger to the casing space behind the plunger, the blocking device (22,23,29,31) comprising a release pin (22) arranged on the longitudinal axis of the casing (11), said pin being axially displaceable from outside the casing and having at its inner end a head (23) controlling an axial bore (31) of said blocking device, said pin thereof being guided in two base portions (19,20) which include a deflector chamber (21) between them, said base portions bounding the corresponding end of the casing, (11) said casing consisting of two concentrically telescoped steel tubes (12,13) forming a by-pass chamber (34), the deflector chamber (21), by the release pin (22,23), being brought into communication through said axial bore (31) with a casing space (28) ahead of the plunger means (16) and being connectable through at least one axial opening in one of said base portions (36) to the by-pass chamber (34), and the latter being connectable through radial bores (43) and an annular chamber (41) of a plug in the first mentioned end of the casing to the casing space (42) behind the plunger means (16).

2. A lifting device according to claim 1, wherein the pin is provided between seals with an annular groove (29) having two outwardly widening truncated conically shaped side walls (30), the inner base portion (20) having a coaxial bore (31) adjoining the respective seal and of a diameter greater than that of the shank of the release pin.

3. A lifting device according to claim 1, wherein the firstmentioned ends of the tubes are connected in substantially similar manner to a plug (15) which is common to both tubes and which carries a seal (39) for the piston rod (18), plunger or the like of the piston (16), all of the connections being constructed and arranged in a gas and liquid-tight manner.

4. A lifting device according to claim 1, wherein the plug (15) is connected by at least one of said radial bores (43) with the by-pass chamber (34) extending beyond the fixing region of the inner steel tube (12) on the plug (15).

5. A lifting device according to claim 1, wherein the deflector chamber (21) extends into the inner base portion (20) and between the two base portions (19,20) of the double base portions (14) and is connected by at least one axial bore (31) with the bypass chamber between the two steel tubes (12), (13) ofthe housing (11).

6. A lifting device according to claim 1, wherein the release pin is guided by seals (22) in the base portions, said seals being formed by a sealing ring with a rectangular cross-section extending parallel to the axial direction, the ring surface facing the deflector chamber (21) being recessed in substantially V- shaped in such a way that the inner ring wall surrounding the release pin has a lesser height than the outer ring wall for reducing friction. 

1. A continuously adjustable lifting device for table tops, chair seats or the like, comprising a tubular casing containing a gas and/or liquid filling, a rod plunger means sealed in and protruding from an end of said casing, a blocking device operable from outside said casing and being arranged at the other end of said casing for locking said rod plunger means relative to said casing in an adjustable position, said blocking device provided in an overflow opening for the filling of the casing connecting the casing space before the plunger to the casing space behind the plunger, the blocking device (22,23,29,31) comprising a release pin (22) arranged on the longitudinal axis of the casing (11), said pin being axially displaceable from outside the casing and having at its inner end a head (23) controlling an axial bore (31) of said blocking device, said pin thereof being guided in two base portions (19,20) which include a deflector chamber (21) between them, said base portions bounding the corresponding end of the casing, (11) said casing consisting of two concentrically telescoped steel tubes (12,13) forming a by-pass chamber (34), the deflector chamber (21), by the release pin (22,23), being brought into communication through said axial bore (31) with a casing space (28) ahead of the plunger means (16) and being connectable through at least one axial opening in one of said base portions (36) to the by-pass chamber (34), and the latter being connectable through radial bores (43) and an annular chamber (41) of a plug in the first mentioned end of the casing to the casing space (42) behind the plunger means (16).
 2. A lifting device according to claim 1, wherein the pin is provided between seals with an annular groove (29) having two outwardly widening truncated conically shaped side walls (30), the inner base portion (20) having a coaxial bore (31) adjoining the respective seal and of a diameter greater than that of the shank of the release pin.
 3. A lifting device according to claim 1, wherein the first-mentioned ends of the tubes are connected in substantially similar manner to a plug (15) which is common to both tubes and which carries a seal (39) for the piston rod (18), plunger or the like of the piston (16), all of the connections being constructed and arranged in a gas and liquid-tight manner.
 4. A lifting device according to claim 1, wherein the plug (15) is connected by at least one of said radial bores (43) with the by-pass chamber (34) extending beyond the fixing region of the inner steel tube (12) on the plug (15).
 5. A lifting device according to claim 1, wherein the deflector chamber (21) extends into the inner base portion (20) and between the two base portions (19,20) of the double base portions (14) and is connected by at least one axial bore (31) with the by-pass chamber between the two steel tubes (12), (13) of the housing (11).
 6. A lifting device according to claim 1, wherein the release pin is guided by seals (22) in the base portions, said seals being formed by a sealing ring with a rectangular cross-section extending parallel to the axial direction, the ring surface facing the deflector chamber (21) being recessed in substantially V-shaped in such a way that the inner ring wall surrounding the release pin has a lesser height than the outer ring wall for reducing friction. 